The invention relates to an apparatus for attaching a valve bag to the filling spout of a filling machine. Valve bags are intended to be filled with pourable material, especially with finely grained pourable material such as cement, and the apparatus includes a storage container for holding a supply of valve bags. The apparatus further includes means for receiving a bag to be attached, as well as means for opening the valve portion of the bag. The receiver means and the opening means are attached to a pivotal arm which picks up the bags, one at a time, opens their valve and thereafter mounts them on the filling spout.
The invention further relates to a filling machine for filling valve bags with finely grained pourable material such as cement, which rotates about a vertical axis and whose circumference is provided with several, mutually displaced filling spouts on which valve bags are mounted to be filled.
Nowadays, the filling of bags with finely grained materials such as cement is almost always done with the aid of filling machinery which has several filling spouts through each of which the material is delivered to a particular bag. The bags which are usually employed are so-called valve bags which are almost always made of paper of different strength, but could, in principle, be made, for example of plastic such as polyethylene.
A valve bag of this type has a front side and a back wall as well as a bottom and a top. When the bag is stored, the bottom and top portions of the bag are folded over and attach to the front or back wall. The top of the valve bag is similar to its bottom, i.e. it is substantially closed on all sides, but in the end portion of the top, near one of the edges of the bag, there is provided a filling aperture which is also called a "valve", from which this type of bag derives its name. In the vicinity of the valve, the top of the bag is provided with a tab which gives it a double-walled configuration through which the filling spout is inserted. When the bag is being filled, the material poured into the bag rises toward the top and eventually pushes the tab located underneath the main top surface upwardly, so that when the bag is removed from the filling spout, it is in a substantially closed, filled-up condition.
Even at the present time, the valve bags described above are mounted on filling spouts of filling machines mostly by hand. It is obvious that the above described process requires substantial manual labor and is correspondingly expensive. In principle, the repetitive nature of the process of mounting such bags suggests mechanization but, apparently, the properties of the valve bags whose shape is not stable and the properties of the filling material have been such that this process has had to be performed mostly by hand.
Further, it is to be noted that, in the first instance, a valve bag must be taken from the storage container and must then be manipulated in a certain manner prior to being mounted on the filling spout. This manipulation includes, firstly, bending the top of the bag up from its normally parallel storage position, in which it attaches to the front or back wall of the bag, and, subsequently, opening the valve by lifting or spreading apart of the two top regions of the bag which form the valve.
Yet it is not alone for reasons of costs that the manual operation is extraordinarily unsatisfactory. For in addition, the filling machines used nowadays (and this is equally true for series construction or carousel type construction), have such short cycling times (i.e., substantially filling times), that they cannot be fully utilized and exploited by servicing the spouts by hand even though short filling times are extremely desirable for reasons of economy. This condition is especially prevalent when a single operator is required to service several filling spouts, which is usually the case. The result is not only poor exploitation of the capabilities of the filling machine, but, because a manual operation is necessarily somewhat irregular, the delivery of filled-up bags also becomes irregular and it is unavoidable that, at times, two or sometimes even more filled-up bags topple over one another on the conveyor means associated with the filling machine.
Therefore, it has recently been attempted to perform the bag mounting process by machine. For example, a mounting apparatus has been disclosed in which bags, which are stored in the storage container in a position in which their front and back walls are essentially horizontal, are lifted at the middle from below by lifting means so as to obtain a substantially flat top surface of the stack of bags in the container. This step is required because the bags are thicker at the end and at the top than they are in the middle. Located above the bag storage container is a receiver head with two slides which are movable in the horizontal plane. When a bag is to be grasped, the head is lowered onto the stack of bags. Subsequently the two slides are extended laterally until they enter the fold between the back of the bag and its bottom or its top, respectively. Subsequently, the head is lifted up again. In the raised position of the head, one of the slides is turned up by 90.degree. so that the bag assumes an L-shaped configuration and is now located at some considerable distance from the stack of bags in the container. Subsequently, the raised head is moved into a claw which, when it closes, grasps the bag adjacent to its top and opens the valve. The claw then removes the bag from the apparatus, thus disengaging the bottom of the bag from its associated slide so that the horizontal portion of the bag flops down. Finally, the gripper claw pushes the bag onto the filling spout and releases it, terminating the mounting process.
The above-described movements of the individual members of the known apparatus must then be repeated in the opposite sense to complete the entire cycle, and the gripping claw must thus re-enter the apparatus. Subsequently, the head must be returned, the turned-up slide must be lowered, and the entire head must be lowered as well. Finally, the slide must be retracted into the head. These individual movements are effected by means of a suitably complicated pneumatic actuating system which performs all the required control functions.
Thus it will be appreciated that this relatively complicated series of movements is not only correspondingly costly, but a necessarily considerable amount of time is required to complete the bag-mounting process, since certain minimum times to perform the individual mechanical movements simply cannot be reduced.
A further disadvantage of this known apparatus is that the control elements, the drive means, and all the other movable parts cannot be sealed with respect to the exterior because the final movement is that of the gripper claw which holds the bag leaving the apparatus. This exposure leads to quite serious disadvantages. For, during the operation of the machine, it is unavoidable that, occasionally, a bag is either intrinsically faulty or that it bursts during the filling process, and in that case, filling material is necessarily blown directly into the bag-mounting apparatus, at least temporarily. When the filling material is cement, for example, this contamination is extraordinarily unwelcome and necessarily leads to operational malfunctions since it is well-known that pneumatic or hydraulic actuators or drive means are extremely sensitive to contamination by such fine grained, pourable material.
For this reason, it has already been attempted to accelerate the working cycle by simplification of the movements and by a reduction in the number of constructional elements, control elements, etc. Thus for example, an apparatus of the above-described type has been disclosed in which several suction cups, disposed on the pivotal arm, are attached to the horizontally positioned top of the uppermost bag within a bag storage container, after which suction is applied so as to remove the particular bag from the stack in the container. Subsequently, the bag is moved into a vertical position so that it may be mounted on the filling spout after its valve means have been opened. The opening of the valve is also performed by suction cups in this known apparatus: the suction cups pull the top of the valve bag upwardly so as to flip the valve open.
It has been shown that even this known apparatus does not meet the demands made of it. For even here, several different movements are still required, each consuming a considerable amount of time, so that the total cycling times are still felt to be too high and do not permit an optimum exploitation of the potential capacity of modern filling machines.
The use of suction cups and vacuum systems brings a substantial further disadvantage, for it is well-known that such elements do not permit satisfactory operation when handling very finely grained material such as cement because this material quickly adheres to the suction cups and the vacuum system and renders them inoperative.